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MIL-STD-1553 David Koppel Excalibur Systems.

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Presentation on theme: "MIL-STD-1553 David Koppel Excalibur Systems."— Presentation transcript:

1 MIL-STD-1553 David Koppel Excalibur Systems

2 Introduction Review of MIL-STD-1553 Specification
WHY? What need does it fill WHAT? What does the spec say HOW? How is it implemented

3 First Session General Background on Avionics Buses
Different Approaches ARINC-429 MIL-STD-1553 Firewire AFDX

4 Second Session Specification Details Message Types Mode Codes

5 Third Session Implementation Issues Prioritizing Messages
Maximizing Throughput

6 Fourth Session Hardware Issues Connections and Terminations
Using an Oscilloscope

7 Fifth Session Software Applications


9 TERMS Avionics Bus Remote Terminal Bus Controller Bus Monitor Source
Sink Data Coupler Dual Redundant Minor Frame Major Frame Message

10 Examples of Clients Altimeter …… Display …… Black Box ……
Flight Computer …… Active Device Passive Device Active and Passive

11 First Generation Analog Devices
One Device Altimeter Speedometer Compass One Display Gauge

12 Second Generation ARINC-429
Multiple Sink Display Auto Pilot Flight Recorder Maintenance Log One Device Altimeter Engine

13 Wiring Diagram Altimeter Display Auto Pilot Engine Flight Recorder
Maintenance Log

14 Military Applications
Multiple Device Missile # 1 Missile # 2 Missile # 3 Missile # 4 Multiple Sink Display Trigger Weapons Test Flight Recorder

15 Military Application ARINC-429 Wiring
Multiple Device Missile # 1 Missile # 2 Missile # 3 Missile # 4 Multiple Sink Display Trigger Weapons Test Flight Recorder

16 Military Applications MIL-STD-1553 Wiring
Mission Computer (Bus Controller) Missile # 1 Missile # 2 Missile # 3 Missile # 4 Display Trigger Weapons Test Flight Recorder

17 1553 Advantages Low Weight Easy Bus Installation Easy to Add RT’s

18 Bus Controller Determines Order of Transmission
Is Source or Sink for almost all Data Can check for bus errors

19 1553 Problem Solution Cable Cut = Crash Inefficiency
Serial Transmission Xmt to / from BC BC Overhead BC Lost = Crash Dual Redundant Bus 1 Mhz speed vs Khz for 429 Minor Frames Backup BC

20 Firewire / AS5643 Used in Video equipment and the F35
Wiring uses a binary tree configuration, each node passes the message through to its other nodes. Requires specialized Link and Phy hardware

21 ARINC-664 Part 7 / AFDX Based on Ethernet Adds dual redundancy
No multiple routes – packets arrive in the order they are sent ~1500 bytes per packet Detection of lost or repeated data Relatively high overhead for short messages

22 Summary Direct lines are simple and cheap
Multiple Transmit/Multiple Sink need a Bus Buses simplify H/W & Complicate S/W

23 Session 2 Goals of MIL-STD-1553 Mindset of MIL-STD Design
Message Types MIL-STD-1760

24 Goals of MIL-STD-1553 Communication between <= 32 Boxes
Low Data Requirement <= 32 Words High Reliability Ability to detect communication errors Ability to retry on error

25 Mindset of MIL-STD Design
Military Approach 1 Commander in Control All others speak when spoken to Commander speaks to one at a time or to all together (Broadcast)

26 1553 Message All Communication is by Message
All Messages are Initiated by the BC All Messages begin with a Command Word

27 Message Types Bus Controller to RT
Bus Controller to All RT’s (Broadcast) RT to Bus Controller Housekeeping messages (Mode Codes) RT to RT Commands

28 Message Format Messages Begin With A Command Word
Data may flow to/from BC from/to RT RT’s return a Status Word

29 Command Word 15 11 10 9 5 4 0 5 Bits 1 Bit 5 Bits 5 Bits
RT Address T/R Bit Subaddress Word Count

30 Command Fields RT Address T/R Bit Address range is 0 - 31
Some Systems use Address 31 as Broadcast T/R Bit If T/R = 1, RT Transmits Data If T/R = 0, RT Receives Data

31 Command Fields RT Subaddress Additional Routing for Complex RT’s
May Correspond to Subsystems Subaddress 0 is for Mode Codes Subaddress 31 is MIL-STD-1553B Mode Code

32 Command Fields Word Count For Mode Codes this is Mode Code Type
Range is 1 to 32 (field value 0 = 32 words) For Mode Codes this is Mode Code Type There are 16 Mode Codes with No Data There are 16 Mode Codes with 1 word of Data

33 Status Word Bit # Description 15-11 RT Address 10 Message Error
8 Service Request 4 Broadcast Received 3 Busy

34 Status Bit Fields RT Address Message Error
Lets BC Know Correct RT is Responding Usually The Only Field Set Message Error Indicates a Communications Error

35 Status Bit Fields Service Request (SRQ) Broadcast Received Busy
Indicates another Subaddress has info ready Used with Get Vector Mode Command Broadcast Received Set in response to the message following a broadcast command Busy When RT can’t respond - discouraged by spec

36 Message Sequence . … . … * * Receive Command Data Word Data Word
Status Word Next Command * . Transmit Command Status Word Data Word Data Word Data Word Next Command * *

37 RT to RT Command … . * * Receive Transmit Tx Status Word Data Word
Rx Status Word . Next Command

38 Mode Commands . . . * * * Mode Command Status Word Next Command
Data Word Next Command . Mode Command Data Word Status Word Next Command *

39 MIL-STD-1760 Features Checksum SRQ Processing Header Word Checking

40 Checksum On selected messages in Bus Controller Mode
On selected RT/Subaddresses in RT Mode For all messages in Monitor Mode

41 SRQ Processing Send Vector Mode Command
If hi vector bit == vector is a status word else send transmit command based on vector word

42 Header Word Checking User selects which subaddress to check
User Selects header value for each subaddress Default is based on 1760 standard

43 Session 3 Implementation Issues Timing Major / Minor Frames
Implementation Examples

44 Timing Issues Intermessage Gap Time Response Time Major Frame
Minor Frame

45 Intermessage Gap Time Time Between Messages
At Least 4 usec Mid Sync to Mid Parity No Maximum in Specification

46 Response Time Time Until RT Sends A Status Word
MIL-STD-1553A Maximum = 7 usec MIL-STD-1553B Maximum = 12 usec

47 Major Frame A Major Frame is the set of all messages in a single cycle
Typical Cycle is 20 to 80 milliseconds Some messages may appear more than once in a single Major Frame

48 Minor Frames 10 Mill 10 Mill 10 Mill 10 Mill ABC AB A AB
Some Messages Are High Priority We can alter frequency of specific messages 10 Mill 10 Mill 10 Mill 10 Mill ABC AB A AB

49 Example: Missile Test Does Pilot Wish To Perform a Test
Instruct Missile to Execute Self Test Get Results Of Self Test Display Results On HUD

50 RT’s in Test Self Test Button on Console RT2 Missile RT3
Heads Up Display (HUD) RT4

51 Message Frame RT2 BC Button to BC BC RT3 BC to Missile
RT3 BC Missile to BC BC RT4 BC to HUD

52 Example: Synchronize RT’s
Synchronize Time Tags for All Terminals Check If Terminal Received the Command

53 Set & Check Synch BC Broadcast Synchronize Mode Command
BC RT1 Last Command Mode BC RT2 Last Command Mode

54 Session 4 Hardware Issues Manchester 2 coding Differential Signals
Bus Termination

55 Manchester Properties
Signal moves between +3.75v and -3.75v Signal always crosses 0v at mid bit Direction of cross determines bit value Data Bits are 1 microsecond mid bit after .5 microseconds Sync is 3 microseconds mid sync after 1.5 microseconds

56 Manchester 2 Coding ‘1’ ‘0’ +3.75v -3.75v microseconds

57 Oscilloscope View Like preceding chart but less square
Original spec has Trapezoidal signal MacAir introduced Sinusoidal signal Fewer harmonics Cleaner signal (less noise)

58 Oscilloscope View – 1553 word
20 us Parity 1 us Sync 3 us Data 16 us

59 Oscilloscope View 1553 message
Response Time Intermessage Gap time RT to BC Transmit Command Status Word Data Word Command Sync Data Sync

60 Differential Signals 1553 Bus is actually 2 wires
The first is Manchester described above The second is the complement of the first During Bus Quiet both lines are 0 volts

61 Advantages Less Dependent On Ground Less Susceptible To Spikes

62 Bus Termination Hi frequency signals are sensitive to reflection
At the end of the Bus the signal can’t continue and tries to “Bounce Back” This is caused by Lo Resistance wire meeting Hi Resistance air

63 1553 Topology Point A, A’ and B represent junctions
RT1 RT2 RT3 BC B B B B A A’ Point A, A’ and B represent junctions We put Terminators on A and A’ to make the bus appear infinitely long This prevents signal reflection

64 Coupling ‘B’ Junctions Represent BC’s RT’s and BM’s Connection To The Bus Two Methods Are Permitted By The Spec Direct Coupling Transformer Coupling

65 Direct Coupling Simple Point To Point Connection
Maximum Stub Length Is 1 Foot (30cm)

66 Transformer Coupling Uses An Isolation Stub Coupler
Filters out DC and Noise Prevents all Reflections May Be Used For Up To 20 Foot (6 m) Stubs

67 The US Air Force Prohibits Direct Coupling on Aircraft
Direct Coupling is convenient when: Used in a lab Connecting Two Boxes Directly


69 Session 5 Software Applications

70 MIL-STD-1553 Applications
Systems Integration RT Development Problem Isolation Post Flight Analysis

71 Systems Integration Run multiple RT’s in Lab
Some RT’s may be ready some not Simulate Bus Controller and some RT’s Simulate Bus timing and errors Monitor responses for timing, quality and correctness

72 RT Development Simulate BC for single message response
Simulate other RT for RT to RT commands Inject errors to check response Alter intermessage timing for stress testing

73 Problem Isolation Reconstruct Bus activity in lab
Selectively simulate RT’s Match bus timing taken from in flight record Perform regression testing

74 Post Flight Analysis Analyze flight data for:
Health analysis – error statistics Throughput analysis Engineering data patterns Indirect data analysis i.e., data comprised of other units, e.g., acceleration = speed Δ / time Correlations between different data elements, e.g. temperature relative to altitude


76 E-mail:
Thank You! Excalibur Systems Phone: Fax:

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